1. Field of the Invention
The instant invention relates to a socket for mounting a printed circuit board and for interconnecting the leads of an integrated circuit in the configuration of a zig-zag inline package to the traces on the printed circuit board.
2. Prior Art
There is disclosed in U.S. Pat. No. 4,060,296, a carrier for interconnecting thereto a dual inline package integrated circuit. The disclosure of the above-referenced U.S. Pat. shows dual leaf contacts mounted within a carrier cavity. Dual leaf refers to the mating configuration between the contact leaves and the package lead, in that there is metal-to-metal contact between the package lead and the socket contact, on both sides of the package lead.
The dual inline package carrier, as disclosed in U.S. Pat. No. 4,060,296, however, was designed for DIP package having leads with lateral spacing on 0.100 inch centerlines, and 0.300 inch width between the opposed leads. Furthermore, a DIP package consists of package leads extending outwardly from sidewalls of the package, the bending downwardly. As the radius in the lead is at the package body, the DIP lead can handle at least 500 grams of insertion force before overstressing the DIP leads.
In the increasing need to preserve printed circuit board real estate, manufacturers of integrated circuit packages have introduced a new configuration known as the zig-zag inline package. The zig-zag inline package body is similar in design to that of the dual inline package, the major difference lies in the lead configuration. The zig-zag inline package leads extend from one side of the package only, every other lead being bent away from the axial centerline in the opposite direction forming two axial rows of leads. The leads on the zig-zag inline package in the same axial row have 0.100 inch centerlines, each lead being laterally offset 0.050 inch from the next offset lead. The distance between axial rows is now 0.100 inch, as opposed to 0.300 inch on the dual inline package. The leads on the zig-zag inline package extend downwardly from the package, are then formed by a first radius projecting the lead outward away from the axial centerline of the package, and then by a second radius bending the lead back towards the axial centerline until the leads are again extending downwardly. The leads of the zig-zag inline package are extremely sensitive to overstress at the first and second radius, overstressing at approximately 270 grams insertion force.
The socket configuration disclosed in U.S. Pat. No. 4,060,296 could not be utilized for the zig-zag inline package. The disclosure of the above-mentioned patent relates to the interconnections for square matrix packages whereas the zig-zag inline package has an offset configuration. Furthermore, as the socket contacts are laterally opposed, the distance between axial rows of contacts was 0.300 inch, and could not be reduced to 0.100 inch with the contacts directly opposed. The contacts as disclosed in the above-mentioned patents could not be utilized for the zig-zag inline package, as the insertion force on those contacts were not predictable enough to consistently maintain below a 270 gram insertion force. The contacts disclosed in U.S. Pat. No. 4,060,296 were formed with the two leaves in contact in a preloaded configuration. As the insertion force is directly related to the contact lead preload, and as the contact leaf preload cannot be consistently held, the insertion force could not be held consistently either.
In order to provide enough current to multiple integrated circuit packages requiring current simultaneously, and to protect the integrated circuit packages from voltage spikes during the package refresh cycle, printed circuit boards typically contain a decoupling capacitor surface mounted to the board, decoupling the package from the power source. The surface mounted capacitor, however, further reduces the printed circuit board space available for integrated circuits as the capacitor requires physical space for the capacitor and printed traces connected to the integrated circuit package leads. If the decoupling capacitors were remotely mounted from the printed circuit board, the printed circuit board would thereby be freed up for mounting integrated circuit package providing for a higher density system.